Precast concrete slabs are well known building materials for applications such as curtain walls, patio stones and floor sections. For example, concrete slabs are known to be provided in large sizes of, for example, twelve feet by eight feet for mounting to the superstructure of a building and to act as an exterior wall for the building. The slabs may be provided with openings and the like therein as, for example, to accommodate windows.
Known precast concrete slabs suffer the disadvantage that the choice of appearances for their external surfaces are limited. More particularly, it is extremely difficult to provide a varying colour or appearance over different sections of the same slab. Typically, expensive, timely and labour intensive processes are required to provide different textures, colours or appearances over different portions of the same slab.